Shaped charge is a major underwater weapon. Its underwater explosion (UNDEX) causes severe damage to underwater structures, such as submarines. It is significant to investigate damage model of typical steel structure underwater by shaped charge. In this paper, the coupled Eulerian-Lagrangian (CEL) method was used based on theory related to UNDEX. Numerical model of curved double-hull steel structure under the effect of shaped charge UNDEX was established. Spatial and temporal evolution of shock wave-projectile-bubble load generated by shaped charge UNDEX was investigated. On the basis of above, damage modes of typical steel structures under the combined shock wave-projectile-bubble load were discussed. Deformation of double-hull structure under different damage elements was compared. Deflections and effective plastic strains at typical points on the structure were analyzed. The results show that shock wave-projectile load cause partial shear breach and small plastic deformation on the structure. The bubble load causes large plastic deformation. Compared with shock wave-projectile load, bubble load produces a 631% increase in deflection for the outer hull, while the inner hull has a 586% increase. Bubble load in shrinkage phase only causes plastic strain on the outer hull.